Luis Pinero-Santiago - The effect of 2-hydroxypropyl-b-cyclodextrin on the excited triplet state of promazine and chlorpromazine

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      Publication Details (including relevant citation   information):

      Journal of Photochemistry and Photobiology A: Chemistry 228   (2012) 44– 50

      Abstract:

      Chlorpromazine hydrochloride (CPZ) is a widely used   anti-psychotic drug that induces skin photosensitization and   photoallergy response after systematic use or topical   applications. The photoallergic mechanism is still unknown.   However, it has been proposed that the triplet excited state   (3CPZ*) could participate in the photodamaging effects. In this   work, we report the photophysical properties of the triplet   excited state of CPZ and its parent derivative promazine   hydrochloride (PZ) in the presence of   2-hydroxypropyl--cyclodextrin (HPC). Absorption measurements   indicate that PZ and CPZ form an inclusion complex with HPC   through a 1:1 stoichiometry. The equilibrium constant at 25 ◦Cis   (2.55 ± 0.09) × 103M−1 and (3.27 ± 0.07) × 103 M−1 for PZ and   CPZ, respectively. The CPZ and PZ triplet excited state   properties changed in the presence of HPC. The triplet lifetime   increases with HPC concentration that is related to the amount of   drug bound. In addition, the triplet intersystem crossing quantum   yield was determined to be 0.45 and 0.17 for PZ and CPZ,   respectively, when more than 95% of the drug molecules are bound   to HPC. Altogether, these results suggest that the   microenvironment plays a crucial role in the 3CPZ* and 3PZ*   properties and thus it can modulate their photosensitizing   effects.

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